Formation of ohmic Ni electrodes on femtosecond laser-modified 4H–SiC surface

The objective of the present study was to investigate the effects of femtosecond laser-induced modifications on the current–voltage (I–V) characteristics between Ni electrodes deposited on laser-irradiated areas on n-type 4H–SiC crystals. We investigated the I–V characteristics and their changes from low-temperature annealing at 400 °C or 500 °C. The I–V characteristics were not the typical Schottky ones, but nonlinear and without a rectifying voltage range even before annealing, and they approached linear with longer annealing durations. An almost linear (i.e., ohmic) I–V curve was obtained for the sample annealed at 500 °C for 18 min. A selected area diffraction pattern taken from the cross section of a laser-irradiated line in the annealed sample was composed of diffraction spots from pure Ni and δ-Ni2Si grains. The coarse-grained Ni2Si phase had an orientation relationship with the SiC crystal, i.e., SiC(0001)//Ni2Si(100) and SiC $$(1\stackrel{-}{1}00)$$ //Ni2Si(013).